Caesar's Bicycle - John Barnes

In an alternate Roman Empire, the ultimate battle is being waged for domination of the multiverse in the epic conclusion of the war for a million Earths

There are a million different Earths across an infinite number of timelines—and every one of them is in peril.

John Barnes's ingenious science fiction saga the Timeline Wars reaches a breathtaking climax in Caesar's Bicycle as former Pittsburgh private investigator–turned–Crux Op agent Mark Strang pursues the alien Closer enemy to a new battleground: an alternate ancient Rome of Caesar and Pompey.

Strang's investigation into the disappearance of a fellow ATN operative has carried him along a new timeline to a Roman Empire at once strikingly similar and remarkably different from the one recalled in history books on his own Earth. What he discovers is a world in the process of radical transformation through the introduction of new technologies, centuries before their time, by both sides in the war for the multiverse—enemy Closers and ATN alike. And this time, Strang's mission carries a new urgency, for the timelines are becoming dangerously unstable and mysteriously starting to close. To prevent the total enslavement of every one of the million Earths, Strang himself will now have to make history. But by ensuring that an infamous assassination actually does take place, Mark Strang could be condemning himself to the most horrible death the Romans ever devised.